To a slow cooker, add the raspberry preserves, sugar, vinegar, Worcestershire sauce, and red pepper flakes, and stir together, using a whisk if you want.

Once combined, remove a 1/2 cup of the mixture and set aside.

Add the meatballs (it's okay if they are frozen) and stir to coat.

Cover and cook on low for 4 hours, or on high for 2 hours.

Using a slotted spoon, remove the meatballs and set aside.

Pour the sauce through a sieve into a small sauce pan. The sieve ensures the sauce is smooth. Some bits of the meatballs just naturally break off into the sauce during cooking in the crock pot. Add the reserved 1/2 cup sauce.

Turn the heat to medium-high and let sauce come to a simmer. Stirring occasionally, let sauce cook until thickened and slightly reduced, about 10 minutes. This will take longer if you doubled the sauce quantities for serving as a main dish.

If you want the sauce a little more spicy, add a dash more red pepper flakes to the glaze at this point.

Once sauce has thickened, add the meatballs back in and stir gently until all meatballs are covered.

Garnish with scallions and/or sesame seeds.

This recipe makes about 60 meatballs as an appetizer and serves 4 as a main dish.